If you can desing the game so that it doesn't matter how wide the player can view. Then allow the user to specify any x,y resolution and just scale everything for y. This way you don't have to lock the window/screen aspect ratio and your sprites still keep their own aspect ratio. You can flip this to work for the other axis too no problem. But if the "field of view" is important then you most likely should either lock the aspect ratio or just post a disclaimer that in non x:y resolutions graphical distortions may occur.